Effects of irradiation using a radioisotope-filled balloon on tissue hyperplasia caused by stent placement in a canine urethral model

Purpose: To evaluate 20 Gy and 40 Gy of intraluminal beta-irradiation using a ¹⁸⁸Re-7mereaptoacetyltriglycine (MAG₃)-filled balloon catheter to reduce tissue hyperplasia caused by covered stent placement for 12 weeks of follow-up in a canine urethral model. Material and Methods: Ten dogs underwent ¹⁸⁸Re-MAG₃-filled balloon dilatation immediately after stent placement; 20 Gy at 1-mm tissue depth in group I (n=5) and 40 Gy in group II (n=5), whereas 5 dogs (group III) underwent conventional balloon dilatation only. Results: There were no significant differences among the three groups for percentage diameter of stenosis, although this was highest in group III. There was a tendency toward lower mean thickness of the epithelial layer and the papillary projection for out-stent area, and thickness of the papillary projection and degree of inflammatory cells for instent area in groups I and II compared with group III. Thickness of the papillary projection in out-stent area was significantly different among the three groups (P=0.031). It was significantly less thick in group I than in group III (P<0.05), whereas group II was not significantly different from group III. Conclusion: ¹⁸⁸Re-MAG₃-filled balloon dilatation has the potential to reduce tissue hyperplasia after 12 weeks of follow-up in a canine urethral model. The use of 20 Gy compared to 40 Gy did not show significant differences.